Switched-mode DC-DC converters are commonly used to provide the voltage required for operating electronic circuits from a differing supply voltage with minimal losses. An example of a DC-DC converter 101 (in this case a buck converter, configured to reduce the supply voltage) is depicted in FIG. 1. Although a buck converter is shown in FIG. 1, it is to be understood that the discussion below applies to any converter configuration.
In the configuration shown in FIG. 1, the series switch (hereinafter SW1) and the shunt switch (hereinafter SW2) are alternately closed in order to provide a varying output voltage to the load. Simplified control waveforms for the switches are depicted in FIG. 2. When the series switch SW1 is on, current flows from the input voltage through SW1 to the output inductor Lout. When the series switch SW1 is off, and the shunt switch SW2 is on, the inductor draws current from the ground node through SW2, which acts as a synchronous rectifier. (It is also possible to have the current decrease to 0 or become negative during this portion of the operating cycle.) The duty cycle D is defined as the proportion of time during which SW1 is on:
  D  =            T      on                      T        on            +              T        off            
In normal steady-state continuous-mode operation, when parasitic losses can be neglected, the output voltage is proportional to the duty cycle:Vout=DVin 
If both switches are on simultaneously, current can flow through them directly from the input voltage supply to ground. This “shoot-through” current can be very large, since its only impediment is the on-resistance of the switches. Shoot-through current does not flow through the load and so is wasted, degrading the efficiency of the converter. Therefore, shoot-through is to be avoided. In order to accomplish this end, “dead times” are normally provided at the end of each switch on-time, during which both switches are off.
During the dead times (shown in FIG. 2 as DT1 and DT2), current continues to flow due to the influence of the typically large-value output inductor Lout. Since both switches are open, this current will charge or discharge the parasitic capacitance of the switch node, which is typically small. As a consequence it is often the case that the potential at the switch node VSW, hereinafter referred to as the switching voltage, changes rapidly during the dead times.
It is desirable to have methods and apparatuses for adjusting dead times of a voltage converter to accommodate for drive circuit asymmetries and dead time disparities.